GNSS Accuracy: Lies, Damn Lies, and Statistics Jan 1, 2007 By: Frank van Diggelen

This update to a seminal article first published here in 1998 explains how statistical methods can create many different position accuracy measures. As the driving forces of positioning and navigation change from survey and precision guidance to location-based services, E911, and so on, some accuracy measures have fallen out of common usage, while others have blossomed. The analysis changes further when the constellation expands to ombinations of GPS, SBAS, Galileo, and GLONASS. Software scripts, provided online, help bridge the gap between theory and reality.

PowerDown Achieving Low Energy-Per-Fix in Cell Phones Jul 1, 2006 By: Wayne Ballantyne, Gregory B. Turetzky, Gary Slimak, John Shewfelt

Reducing the energy-per-fix (EPF) to a minimum is key for LBS, as continuous tracking shortens cell-phone battery life. This article focuses on realizing a low-current RF front end, minimizing RF active time, and developing an intelligent GPS middleware layer to determine whether a low EPF is likely or necessary.

Wireless Choices for LBS — Control Plane and User Plane Architectures Mar 2, 2006 By: Arnold Gum, Kirk Burroughs

The choice between two standardized architectural approaches to deploying A-GPS location services control plane and user plane can influence the quality, applicability, and success of the service offering. Differing requirements for both voice-centric and application-centric applications drove the need for two different location architectures, which provide operation tailored to two different types of needs.

Myths and Realities of Anywhere GPS High Sensitivity versus Assisted Techniques Sep 1, 2005 By: Chris Carver

AGPS does not mean works "Anywhere" GPS. Accurately determining what will work for any given application requires a properly designed test procedure.